1. Technical Field of Endeavor
The invention, in its several embodiments, generally relates to lighting systems based on Light Emitting Diodes (LEDs), and more specifically to a method and apparatus of controlling intensity and perceived color temperature of one or more LED clusters or triplets in order to provide a display of different colors as perceived by a person, and still more precisely, to effect various colors and display patterns from an array of LEDs based on time sensitive on-off switching.
2. State of the Art
LEDs may be employed to produce a lighting system with a varying color scheme, which is often desired for applications such as lamps, back light sources, traffic signals, display boards, illuminating switches and commercial lighting. LEDs are available in basic colors that comprise red, green and blue (RGB), and other colors can be generated for human perception by manipulating the intensity of individual LEDs of a cluster of at least three LEDs comprising each of red, green and blue.
U.S. Patent Publication Number US 2004/0207334 by Lin discloses a system for a color-changing bulb for the instrument panel of a vehicle, which is made as a bulb and directly installable in a bulb seat of the instrument panel. The color-changing bulb includes a bulb housing defining a receiving space for receiving a light emitting diode and a circuit board. The LED includes three LED chips for generating red, blue and green light components. A controlling circuit is disposed on the circuit board and connected with the LED for driving the three-color LED chips to emit light. By use of a brightness adjustment switch on the instrument panel or a headlight switch, at least seven combinations of colors of light can variably emitted. The Lin publication also discloses a memory unit to store or count the number of times the headlight switch is switched to create additional signals indicating which color the LED system should effectively produce in the sense of human perception. This system is disclosed as having a stabilizing unit and a digital cycle outputting unit.
U.S. Patent Publication Number US 2002/0047628 by Morgan et al., discloses a system applicable for outdoor decorating retail, commercial and residential places.
U.S. Pat. No. 5,420,482 to Phares, discloses a color display apparatus in which each of the three-color LED unit in a circuit are driven by transistor biasing. In this system, each transistor base is coupled to a respective latch resistor. Also, the biasing of the transistor according to Phares may be changed by changing the grounding resistor of the potential divider.
U.S. Pat. No. 6,016,038 to Mueller, et al., discloses a pulse width modulated current control for an LED lighting assembly, where each current-controlled unit is uniquely addressable and capable of receiving illumination color information on a computer lighting network. The light module of Mueller may be interchanged with other light modules having programmable current and maximum light intensity ratings. Muller, et al., teaches the use of a computer controller to operate the pulse width modulated LED lighting assembly.
U.S. Pat. No. 6,150,774, also to Mueller, et al., discloses a pulse width modulated current control for an LED lighting assembly wherein each current-controlled unit is uniquely addressable and capable of receiving illumination color information on a computer lighting network. The use of a manual control for an LED lighting assembly is disclosed.
U.S. Pat. No. 6,211,626 to Lys, et al. discloses a light module having an LED system for generating a range of colors within a color spectrum, a processor for controlling the amount of electrical current supplied to the plurality of light emitting diodes, so that a particular amount of current supplied thereto generates a corresponding color within the color spectrum, and a housing within which the LED system is positioned.
U.S. Pat. No. 6,340,868 to Lys, et al. discloses a computer controlled multicolored lighting network comprising a light module having a plurality of light emitting diodes for generating light for a range of colors within a color spectrum, a processor for controlling the amount of electrical current supplied to each light emitting diode such that a particular amount of current supplied to the light module generates a corresponding color within the color spectrum, and a power module for providing electrical current from a power source to the light module, where the power module includes a connector for removably and replaceably connecting the power module to the light module.
U.S. Pat. No. 6,528,954 to Lys, et al. also relates to LED lighting assemblies, and discloses the use of a processor to control current through the LEDs.
Decorative lighting via a controlled lighting system is disclosed in U.S. Pat. No. 4,317,071 to Murad in which three circuits are disclosed as directly connected to one or more lighting element of a particular color.